A strap assembly worn by a player in a sitting or standing position for supporting a guitar or similar instrument in a generally horizontal face-up position, stabilizes the instrument while it is being played without impeding freedom of movement of the player's hands. The strap assembly includes an elongate shoulder strap, a shoulder pad slidably mounted on the shoulder strap, an instrument headstock strap releasably connected to a first end of the shoulder strap having a looped end for attachment to the instrument headstock, an instrument body strap releasably connected to a second end of the shoulder strap for attachment to the body of the instrument, and a forearm loop mounted on the instrument body strap for receiving the forearm of the picking-hand of the instrument player.